Portable compact disc players consume large amounts of power to drive the servo motor and laser pickup or tracking mechanism of the player. The servo motor rotates the disc, while the laser pickup or tracking mechanism moves the laser along a pair of rails to read the rotating disc. The battery life of a portable CD player is limited by the mechanical action of the player. The battery life of a typical portable CD player may be as little as fifteen hours on two AA batteries. During the playback of an audio CD player, the disc is rotated continuously rotated so that data is read from the compact disc at a constant bit rate of 1.4 Mb/s or greater.
A compact disc may be formatted to include compressed audio content, such as MP3 files or any other suitable compressed audio format. In the case of the MP3 compressed audio format, as many as 400 music files or songs can be placed on a single compressed audio CD. A CD that includes compressed audio files can be played on a CD player that is configured for the playback of compressed audio files formatted on a CD disc. CD players of this sort include CD-ROM players and hybrid CD players that can play both traditional CDs and CD-ROMs that include compressed audio files. Regardless of the particular compact disc format, CDs that includes compressed audio files are referred to herein as compressed audio CDs.
A compressed audio CD that includes MP3 files can be encoded at a bit rate of between 32 and 320 kb/s, with a typical bit rate of 128 kb/s. Because the mechanical and algorithmic structure of any CD player dictates that the data be read from the disc at a rate of 1.4 Mb/s or greater, a CD player that is playing a compressed audio CD that includes a group of MP3 titles will typically read in data at a rate that is faster than necessary to play the CD. The data is read in by CD played at a rate of 1.4 Mb/s and excess data will be cached in the local memory of the CD player. As such, the CD player receives data at a bit rate that is much greater than the bit rate necessary for the CD to store and process the data for playback. Although the CD player caches data received from the CD, the cache space is limited.